The invention relates generally to a seat and more particularly but not exclusively a seat for a vehicle.
One form of seat which is adjustable in respect of height comprises a seat portion which is supported relative to a base frame by means of a support arrangement consisting of two pairs of support arms at respective sides of the base frame. Each pair of support amrs comprises first and second arms which intersect each other at a position intermediate their ends, thereby defining a scissor-like configuration. The first end of each of the arms is connected slidably to either the seat portion or the base frame while the second end of each of the arms is non-slidably connected to the base frame or to the seat portion respectively. The seat structure further includes a cam lever which is connected rotatably to the non-slidable ends of the arms, at the seat portion or the base frame respectively, and a slider which is mounted slidably in the longitudinal or fore-and-aft direction of the seat and which with its one end acts on the cam lever to cause rotary movement thereof upon sliding movement of the slider. A spring has one end fixed to the slider and the other end connected either to the seat portion or to the base frame respectively, for supporting the seat portion relative to the base frame The spring is thus operable to urge the seat portion upwardly, to carry the weight of a seat occupant. The seat further includes an arrangement for adjusting the height of the seat portion.
Such a seat is set forth for example in British patent specification No 965 072 or German published specification (DE-AS) No 24 46 516. In that structure, adjustment in respect of the height of the seat is effected by altering the angle between the non-slidable ends of the arms and the cam lever which is connected thereto. However, the fact that the cam lever is to be rotatable relative to the arms involves a substantial amount of mechanical structure to achieve that aim. Furthermore, the arrangement requires a strong locking or detent means to secure the cam lever with respect to the corresponding ends of the arms, once adjustment of the angle between the cam lever and the arms has been effected.